1. Field of the Invention
This invention relates to an ink tank, an ink jet recording apparatus mounting the ink tank, and a package for the ink tank, and more particularly to a readily recyclable ink tank excellent in visual perceptibility, an ink jet recording apparatus mounting the ink tank, and a package for the ink tank.
2. Related Background Art
An ink jet recording apparatus discharges ink from recording means (a liquid discharge head) onto a recording medium to thereby effect recording, and have come into wide use in these several years because of its advantages such as being easy to make the recording means compact, being small in noise because of a non-impact type, and color images being easily formable because a variety of inks can be used.
With the spread of the ink jet recording apparatus in recent years, an increase in the quantity of ink used has been required.
So, recently, in order to improve the ink containing efficiency and the use efficiency, a construction as disclosed in Japanese Patent Application Laid-open No. 6-40041 wherein about a half space of the interior of an ink tank is filled with an ink absorbing material, and a construction as disclosed in Japanese Patent Application Laid-Open No. 9-267483 wherein an ink tank of multi-layer structure is used and an inner wall layer fluctuates with the use of ink and the ink is held by the reaction force thereof have been proposed and partly put into practical use.
Such an ink jet recording apparatus, because of its structure in which the ink is discharged to thereby effect printing, suddenly becomes incapable of printing when the ink in the ink tank becomes exhausted and therefore, it is desirable that the quantity of ink remaining in the ink tank be detectable. Therefore, an ink tank constituted by a transparent or translucent member transmitting visible light therethrough so that a user actually utilizing the apparatus can directly visually perceive the quantity of ink has been put into practical use. This also has the advantage that before the apparatus is loaded with an ink tank, what color of ink is contained in the ink tank can be easily confirmed.
Actually, there is a case where besides the detection of the quantity of remaining ink by the user's visual perception, optical type means for detecting the quantity of remaining ink is provided on the apparatus side. This means for detecting the quantity of remaining ink applies light from the outside of the ink tank to an ink storing portion, and detects the quantity of remaining ink by the difference in the intensity of the transmitted light or the reflected light thereof due to the presence or absence of the ink. Accordingly, to adopt this optical type detecting means, it is necessary for the ink tank to transmit visible light therethrough, and if only the ink tank thus has transmissively for the visible light, it is possible to incorporate this optical type detecting means relatively easily, and the error is small and the ink component is not affected.
In recent years, regarding images outputted by the ink jet recording apparatus, a photographic tone quality of image has been pursued and a higher quality of image has been required. Along therewith, the development of inks or the like having an excellent coloring property and weatherability has been advanced. As one of methods for realizing this photographic tone quality of image, a method of using ink of a lighter color than ordinary ink so that the feeling of stay of ink droplets discharged onto a recording medium such as paper may not remain, and moreover giving harmony to the print has been put into practical use.
However, when the ink of such a light color is contained in the aforedescribed conventional ink tank and is kept in custody and used, the color tone thereof may be deteriorated with the lapse of time. Particularly, ink having its dye density reduced to 1/5 or 1/10 as compared with conventional ink was poured into the ink tank and a fading resistance test was carried out with the result that the hue, chroma and brightness of the ink may change and a desired color tone may not be obtained.
This phenomenon came to be recognized as the result of the fact that the time for which the ink tank is mounted on the recording apparatus became long with an increase in the quantity of ink usable by an ink tank. Also, as the result of the spread of the ink jet recording apparatus, the ink tank which is an article of consumption is kept in custody under various environments, and even In ink tanks long displayed in stores, such a task has come to be recognized.
We have assiduously studied about this phenomenon to find that the ink contained in the ink tank having a light-transmitting property was exposed to ultraviolet rays and much of an ink dye dissolved therein was decomposed and changed in quality and the quantity residual while remaining the original dye decreased and the substantial density of the dye was reduced. It has therefore been found that a phenomenon called discoloring which means that a color becomes lighter occurs.
Moreover, of a plurality of colors (usually four colors or six colors) forming the color, the degree of influence of ultraviolet rays differs depending on the colors and the structure of dyes and in addition, the time for which the ink tank is exposed to ultraviolet rays varies from color to color depending on the hysteresis of use after the ink tank has been unsealed. Therefore, in some cases, the colors become generally discolored or only one color is discolored and the color balance is destroyed. Particularly, a change in which discoloring takes place gradually is a change difficult for most users to discriminate just as the CRT of a television becomes deteriorated, but when an ink tank used up has been interchanged, the problem we point out is remarkably recognized. That is, when printing has been started from an old ink tank in which dye components tend to discolor and that ink tank has been interchanged with an ink tank in which discoloring is hardly noticed to thereby effect continuous printing, prints which are the objects of comparison are near at hand and therefore, the recognition that the color is unusual cannot be avoided.
Now, a tank colored by the use of inorganic pigments or organic pigments and a tank increased in rigidity with a filler added thereto are shielded from ultraviolet rays. Such a construction, however, has not been desirable because the detection of the remaining quantity (presence or absence) of ink by the above-described optical detection of the remaining quantity is often difficult and the use is limited from the viewpoint of the recycle of the material.
Further, considering the form during sale, like the visual perceptibility of the ink contained in the ink tank is required, it is also desirable in a commodity package that a commodity (ink tank) therein can be seen. In such a case, among versatile resins, PS and PET are mentioned as typical transparent package materials, and with regard to these, regenerated materials are also circulated. However, PS is poor in a steam barrier property and therefore is liable to suffer from the problem that the ink evaporates and the density of a coloring material therein rises. PET has particularly the weak point that it is invaded by steam (ammonia) produced by the decomposition of urea prescribed for the prevention of the solidification and drying of the ink, and at least a package in the form of a bag has suffered from a problem.